Certain surgical procedures require the use of a sighting device. For example, when an intramedullary nail is inserted in the medullary canal of a bone, it may be necessary to lock the end of the nail in place by inserting retaining pins, also called interlocking screws or studs, through interlocking holes at the distal end of the nail. It is important in inserting these studs that one should know the precise position of the interlocking holes in the nail to avoid unnecessary damage to the bone.
Devices are known in which a drill template is adjusted and ultimately fixed in the desired position by means of an x-ray image amplifier. For example, Swiss Pat. No. CH-A5 635 998 discloses an aiming device which has an aiming head with a hole for the insertion of a directional socket. The aiming head mounting is positioned in a holder that is connected to the x-ray machine and is suspended from the x-ray machine. This arrangement makes it difficult to position the apparatus and to fix it in position, with resulting unsatisfactory target precision. In addition, the stationary arrangement limits operation.
Because of these problems, an aiming device has been devised that can be used independently of the x-ray machine. Thus, German industrial design Pat. No. U1 84 17 428 describes a device with a receiving head that rests in a holder and is permeable to x-rays, and which accepts a drill bit or a drill wire. Even this improved device, however, has major disadvantages. In particular, the aiming process takes place during the drilling of the bone, which causes considerable darkening of the working field and low image resolution. Also, the lack of a drill housing to protect the patient's tissue leads to damage whenever the tool or instrument being used is changed.
In addition, all known devices suffer from a serious flaw in that it is impossible to verify the targeting procedure and to make the necessary corrections during the operation.